Can you find out the missing number in the grid?

What is the relationship between these matchstick pictures below?

What can you hold in your right hand, but never in your left hand?

You along with your friend are standing in front of two houses. Each of those houses inhabits a family with two children.

Your friend tells you the below two facts:
1) On your left is a family that has a boy who likes accounts but the other child loves science.
2) On the right is a family with a seven-year-old boy and a newborn baby.

You ask him, "Does either of the family have a girl?"

To this, he replies, "I am not quite sure. But can you guess that? If you are right, I will give you $500."

Which family do you think is likely to have a girl?

You are in a room with no metal objects except for two iron rods. Only one of them is a magnet.
How can you identify which one is a magnet?

Count the number of squares in the picture below.

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

An express train takes 3 seconds to enter the tunnel which is 1 km long.
If it is travelling at 120 km an hour, how long will it take to pass completely through the tunnel?

Find the next number in the following series:
6, 14, 26, 98, __?

Before Mount Everest was discovered, what was the highest mountain in the world?